A solar panel is a packaged interconnected assembly of solar cells, also known as photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. The power that one solar panel can produce is seldom enough to meet requirements of a home or a business, so the solar panels are linked together to form a solar panel array. Most solar panel arrays use an inverter to convert the DC power produced by the modules into alternating current that can power lights, motors, and other loads. The solar panels in a solar panel array can be connected in series to obtain the desired voltage and then the series coupled groups of panels can be connected in parallel to allow the system to produce more current.
For optimum efficiency, the solar panels should be in perpendicular alignment with the light rays of the sun. However, since the earth is constantly rotating, a fixed solar panel may be oriented to be perpendicular to the sun light at approximately noon each day. Each solar panel in the solar panel array can be attached to a fixed mount that tilts the solar panel to face due South in the Northern Hemisphere and conversely, the fixed mount can tilt the solar panel to face due North in the Southern Hemisphere. The tilt angle can be varied for season, but if fixed, should be set to give optimal array output during the peak electrical demand portion of a typical year.
In order to improve efficiency, some solar panel arrays can track the movement of the sun through each day to greatly enhance energy collection. These tracking systems may move periodically to optimize the tilt angle so that in the morning the solar panel can face East and in the afternoon, the solar panel can face West. Solar panel tracking devices add cost, and require maintenance, but can also significantly improve the efficiency of the solar panel array. For large solar panel arrays, the energy gained by using tracking systems outweighs the added complexity and can increase efficiency by 30% or more compared to fixed systems.
Solar panel electrical output is extremely sensitive to shading. When even a small portion of a solar panel or solar panel array is shaded, while the remainder is in sunlight, the output falls dramatically due to internal “short-circuiting” which results from the electrons reversing course through the shaded portion of the p-n junction. If the current drawn from the series string of solar cells in the solar panel is no greater than the current that can be produced by the shaded cell, the current and power developed by the string is limited. If enough voltage is available from the rest of the cells in a string, current will be forced through the cell by breaking down the junction in the shaded portion. Thus, instead of adding to the power produced by the solar panel, the shaded cell(s) in the solar panel absorbs power, turning it into heat. Since the reverse voltage of a shaded cell is much greater than the forward voltage of an illuminated cell, one shaded cell can absorb the power of many other cells in the string, disproportionately affecting panel output. For example, a shaded cell may drop 8 volts, instead of adding 0.5 volts, at a particular current level, thereby absorbing the power produced by 16 other cells. Therefore, it is extremely important that in a solar panel array installation none of the panels is shaded at all by an adjacent solar panel.
It is desirable to have the solar panel array occupy a minimum amount of land. However, for the reasons discussed above, each solar panel must not cast a shadow on any portion of the adjacent solar panels in order to prevent the short-circuiting described above. Each of the solar panels in the solar panel array is mounted to a piling that is driven into the ground and provides a stable support structure for the solar panel. Thus, the positions of the pilings determine the positions of the solar panels in the array of panels. Because the positions of the panels are critical for space and operating efficiency each piling must be precisely positioned. A typical array can include 980 to 1,250 foundation pile.
In order to position each piling accurately, a survey crew which can typically include two workers are required to determine the exact location of each piling. After the piling locations are determined, a plate lay-out crew may be required to place guild plates over each piling location. The plate lay-out crew may require four workers who position and then stake each guild plate in place at each piling location of the solar panel array. The staking of the plate can require a significant amount of force to swing a sledge hammer to drive the stakes in place and can result in hand injuries. An alignment crew may also be necessary to adjust the alignment of the pilings. After they are driven.
The typical foundation of a solar panel array system consists of 12′ to 20′ long piles which can be pipe with a circular cross section, I-beam or other cross sections that can be driven into the ground using a pile driver. Driving piles, as opposed to drilling shafts, is advantageous because the soil displaced by driving the piles compresses the surrounding soil, causing greater friction against the sides of the piles, thus increasing their load-bearing capacity. A solar panel can be mounted on each of the driven piles. A solar array system can have about 1,000 piles per mega watt. There are other techniques for producing the solar panel array foundations, but a driven pile is more cost efficient verses other techniques like poured in place concrete and concrete ballast system which can be about ten times more expensive.
One method the piles can be aligned in an array using stringing lines tape measures. The laser can mark a straight line that the pilings can be aligned with. Once the laser is used to identify a point, a string line is pulled to create a reference line that should be straight along the laser line. The string line can be stretched across a portion of the solar array land to create a reference line for aligning the pilings. However, a problem with string lines is they move in the wind even while under tension. A cross wind can cause the string line to curve and when pulling a string line over 100 feet, the line may not be straight. All solar arrays, the pilings have to be within ¼ inch of side to side alignment and within ¼ inch of the designated height. Setting the pilings with the string lines and tape may not be able to provide the required level of accuracy.
Another method for properly positioning each piling is surveying every piling point for a solar panel array. After each survey, each piling point is marked with a nail and ribbon. The ground crew then installs the guide plates at each piling point. The surveying and guide plate installation are not only costly but time consuming as well. In some installations, rain or snow can occur after the survey making it impossible to keep working because the survey points are under water or snow. After the guide plates have been set, an ABI crew installs the piles. What is needed is an improved system for installing the piles for a solar panel array that is more accurate and efficient.